This invention relates to a ride control for a motor vehicle and particularly to such a control which senses the response of vehicle suspension to the road surface and automatically adjusts a variable damper in the vehicle suspension system to maintain a predetermined ride character in vehicle operation.
Very few adaptive ride control systems are shown in the prior art; and those that are shown are limited in their ability to accurately characterize the road surface and thus in the refinement of their ride control. A system typical of this prior art is shown in the U.S. Pat. No. 4,333,668, to Hendrickson et al, issued June 8, 1982, in which the ride control characteristics are varied in response to sensed velocity of movement between the sprung and unsprung masses with comparison of this velocity with a predetermined reference for two possible settings. Other control inputs of the system, such as the roll sensors, are based on operator actions rather than on the character of the road surface. While the velocity sensed by this system gives some rough idea of whether the road is rough or smooth, there are many different road surfaces requiring different damping characteristics for fine ride control which are indistinguishable by velocity between sprung and unsprung masses alone. There are three interrelated factors of the movement between sprung and unsprung masses--velocity, frequency and amplitude--which characterize the road surface. If two of these are known, especially if the two are frequency and maximum amplitude, the road surface can be adequately characterized for finer ride control than is possible in the prior art systems.